Imo in order of importance:
a) you can pot control easier, example: he check, you check
b) you can build pot easier, example: he bet, you raise
c) you have one action more information compared to villain, example: he bets, you can fold if you have nothing, you can call if you have something
d) good villain knows you have positional advantage, thus you have positional advantage + extra fold
equity against him. And against good opponents you need all the help there is. example: CO opens, you 3bet KTo, he folds AJo.
Why I think a) is most importan is just a hunch because when hero is OOP mostly his only option is to bet with TP type
hands, even if board is quite scary. maybe, at least if feels like it. Betting blind....